I have tons of mini nukes. The only problem is that the only weapon that shoots mini nukes is the Fat Man. I've seen it a few places and and never had the caps to buy it. Is there a place in Fallout New Vegas where I can get it for a low price or free?

Quarry Junction - Lying near the edge of a radioactive pool to the west of the quarry. On this map you can select weapons>big guns and you will see 3 markers on the map,one of them is the location for the fat man(Quarry).

Nopah cave - On the corpse of a super mutant master.

On the body of a super mutant master near a cazador nest directly south of Jacobstown.

The Fort - At high player levels one can be found on a legionary blacksmith

Be aware that most of these locations are dangerous for a low level character.

The Gun Runners Arsenal DLC also added a unique variant, named Esther. It's not cheap, but I made a tonne of money by playing through Lonesome Road and selling everything I picked up everytime I hit a Commissary. Made buying Esther simple.
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GShenaniganFeb 7 '12 at 16:33